The present application claims priority and contains subject matter related to Japanese Patent Application No. 2000-367433 filed in the Japanese Patent Office on Dec. 1, 2000, and the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a toner recycling device of electrophotographic image forming apparatuses such as copying machines, printers, facsimile apparatuses, multi-functional apparatuses, etc.
2. Discussion of the Background
An electrophotographic image forming apparatus forms a toner image on a photoconductor by performing charging, optical writing, and developing operations. The toner image formed on the photoconductor is transferred onto a sheet either directly from the photoconductor or via an intermediate transfer member, and thereby an image is recorded on the sheet. After the toner image is transferred onto the sheet, respective residual toner on the photoconductor and the intermediate transfer member are removed by cleaning devices for subsequent image formation starting with a charging operation.
Recently, in such electrophotographic image forming apparatuses, from the view points of effective use of resources, protection of the environment, and reduction of the maintenance expenses, it is widely practiced to recycle residual toner collected by a cleaning device without discarding the collected residual toner. The collected residual toner is transferred to a developing device to be mixed with a new toner for subsequent use.
A known toner recycling device, which recycles residual toner collected by a cleaning device to a developing device, fluidizes and conveys the collected residual toner to the developing device using a powder conveying pump called a Monau pump. In such a toner recycling device, however, if the powder conveying pump is always driven, the airtightness of the powder conveying pump is deteriorated due to abrasion, so that toner scattering is caused, the life of the powder conveying pump is reduced, and the temperature of the pump rises.
Accordingly, a known toner recycling device using a powder conveying pump includes a detecting device to detect the amount of collected toner (e.g., a powder sensor) in a toner reservoir, and is configured such that when the detecting device detects that the collected toner amount has reached a predetermined amount, the powder conveying pump is driven for a predetermined period of time.
The present inventors realized that to eliminate such a collected toner amount detecting device by providing a counting device for counting the number of picture elements of an image which is formed. The picture element counting device counts the number of picture elements of an image which is formed, and based upon the integrated value of the number of picture elements, the toner consumption amount is calculated. When the calculated toner consumption amount reaches a predetermined value, the collected toner amount in the toner reservoir is determined to reach a predetermined amount, and then a powder conveying pump is driven.
In a copying operation in an image forming apparatus, a photocoductor starts to rotate when a sheet starts to be fed from a sheet cassette and continues to rotate until the sheet is discharged from the apparatus. Accordingly, in a one-to-one copying operation in which one copy is obtained from one original, the rotating period time of the photoconductor per one copy is longer than in a continuous copying operation in which a plurality of images are successively obtained from one original. As the rotating period of time of the photoconductor per one copy increases, the background soiling of the photoconductor increases, and thereby causes an increase in toner consumption and consequently an increase in the amount of collected residual toner per one picture element.
The increase in the amount of collected residual toner is significant as the image ratio in an image to be formed is smaller. For example, when the image ratio of an image to be formed is about 5%, the amount of collected residual toner in the one-to-one copying operation is about three to five times of that in the continuous copying operation. That is, depending upon whether the ratio of one-to-one copying operations is greater or smaller than that of continuous copying operations, the amount of collected residual toner greatly varies.
A powder conveying pump is always driven minimally, considering the above-described variation in the amount of collected residual toner. Therefore, generally, the amount of consumed toner per one picture element is set adjusted to the amount for the one-to-one copying operation, and the powder conveying pump is driven when it is detected the toner consumption amount, which is calculated based upon the integrated value of the number of picture elements, reaches a predetermined value.
Accordingly, when the ratio of continuous copying operations is greater than that of one-to-one copying operations, the time when the powder conveying pump is driven unnecessarily increases. Thereby, airtightness of the powder conveying pump is deteriorated due to abrasion, toner scattering is caused, the life of the powder conveying pump is reduced, and the temperature of the pump rises.
Further, the amount of collected residual toner which is conveyed to a developing device by the powder conveying pump varies due to the deterioration of the airtightness of the powder conveying pump, causing instability to the mixture ratio of the collected residual toner relative to a new toner, and consequently decreasing the image quality.
Furthermore, depending upon the density of a toner image, the amount of collected residual toner per one picture element greatly varies.
The present invention has been made in view of the above-discussed and other problems and addresses the above-discussed and other problems.
Preferred embodiments of the present invention provide a novel toner recycling device of an electrophotographic image forming apparatus, in which the amount of collected residual toner is precisely detected in accordance of the copying mode so that a driving interval of a powder conveying pump is enlarged and at the same time the ratio of recycled toner in a developer is made constant so that the image quality is improved.
The preferred embodiments of the present invention further provide a novel toner recycling device of an electrophotographic image forming apparatus, in which the amount of collected toner is precisely detected in accordance of the density of a toner image so that a driving interval of a powder conveying pump is enlarged and at the same time the ratio of recycled toner in a developer is made constant so that the image quality is improved.
The preferred embodiments of the present invention also provide a method of precisely detecting the density of a toner image based upon an objective criterion and of precisely detecting the amount of collected residual toner.
Further, the preferred embodiments of the present invention provide a method of avoiding useless driving of a powder conveying pump so that the life of the powder conveying pump is increased.
According to a preferred embodiment of the present invention, a toner recycling device of an electrophotographic image forming apparatus conveys collected used toner to a developing device of the image forming apparatus. The toner recycling device includes a powder conveying pump that is driven to convey the collected used toner to the developing device of the image forming apparatus when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and an adding device that adds a predetermined constant value to the integrated value when driving of an image bearing member of the image forming apparatus is detected.
According to another preferred embodiment of the present invention, a toner recycling device of an electrophotographic image forming apparatus to convey collected used toner to a developing device of the image forming apparatus includes a powder conveying pump that is driven to convey the collected used toner to the developing device of the image forming apparatus when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and a coefficient determining device that determines a predetermined coefficient according to toner density of a developer of the image forming apparatus and that corrects each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
According to still another preferred embodiment of the present invention, a toner recycling device of an electrophotographic image forming apparatus to convey collected used toner to a developing device of the image forming apparatus includes a powder conveying pump that is driven to convey the collected used toner to the developing device of the image forming apparatus when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, an adding device that adds a predetermined constant value to the integrated value when driving of an image bearing member of the image forming apparatus is detected, and a coefficient determining device that determines a predetermined coefficient according to toner density of a developer of the image forming apparatus and that corrects each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
In the above-described toner recycling devices, the coefficient may be determined according to a difference between the toner density of the developer and a target value for the toner density. Further, the powder conveying pump may be stopped to be driven a predetermined time after having been started to be driven.
According to still another preferred embodiment of the present invention, an electrophotographic image forming apparatus includes a developing device to develop a latent image formed on a photoconductor with a toner, and a toner recycling device that conveys collected used toner to the developing device. The toner recycling device includes a powder conveying pump that is driven to convey the collected used toner to the developing device when an integrated value of predetermined numerical values, each based upon a number of picture elements of an image to be formed, is equal to or greater than a constant value, and an adding device that adds a predetermined constant value to the integrated value when driving of the photoconductor is detected.
According to still another preferred embodiment of the present invention, an electrophotographic image forming apparatus includes a developing device to develop a latent image formed on a photoconductor with a toner, and a toner recycling device to convey collected used toner to the developing device. The toner recycling device includes a powder conveying pump that is driven to convey the collected used toner to the developing device when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and a coefficient determining device that determines a predetermined coefficient according to toner density of a developer of the image forming apparatus and that corrects each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
According to still another preferred embodiment of the present invention, an electrophotographic image forming apparatus includes a developing device to develop a latent image formed on a photoconductor with a toner, and a toner recycling device configured to convey collected used toner to the developing device. The toner recycling device includes a powder conveying pump that is driven to convey the collected used toner to the developing device when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, an adding device that adds a predetermined constant value to the integrated value when driving of the photoconductor is detected, and a coefficient determining device that determines a predetermined coefficient according to toner density of a developer of the image forming apparatus and that corrects each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
In the above-described electrophotographic image forming apparatuses, the coefficient may be determined according to a difference between the toner density of the developer and a target value for the toner density. Further, the powder conveying pump may be stopped to be driven a predetermined time after having been started to be driven. According to still another preferred embodiment of the present invention, a toner recycling method of an electrophotographic image forming apparatus includes driving a powder conveying pump to convey collected used toner to a developing device of the image forming apparatus when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and adding a predetermined constant value to the integrated value when driving of an image bearing member of the image forming apparatus is detected.
According to still another preferred embodiment of the present invention, a toner recycling method of an electrophotographic image forming apparatus includes driving a powder conveying pump to convey collected used toner to a developing device of the image forming apparatus when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and determining a predetermined coefficient according to toner density of a developer of the image forming apparatus and correcting each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
According to still another preferred embodiment of the present invention, a toner recycling method of an electrophotographic image forming apparatus includes driving a powder conveying pump to convey collected used toner to a developing device of the image forming apparatus when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, adding a predetermined constant value to the integrated value when driving of an image bearing member of the image forming apparatus is detected, and determining a predetermined coefficient according to toner density of a developer of the image forming apparatus and correcting each of the predetermined numerical values by multiplying each of the predetermined numerical values by the coefficient.
In the above-described toner recycling methods, in the determining step the coefficient may be determined according to a difference between the toner density of the developer and a target value for the toner density. Further, in the driving step the powder conveying pump may be stopped to be driven a predetermined time after having been started to be driven.
According to still another preferred embodiment of the present invention, an electrophotographic image forming method includes developing a latent image formed on a photoconductor with a toner, and recycling collected used toner to a developing device. The recycling includes driving a powder conveying pump to convey the collected used toner to the developing device when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and adding a predetermined constant value to the integrated value when driving of the photoconductor is detected.
According to still another preferred embodiment of the present invention, an electrophotographic image forming method includes developing a latent image formed on a photoconductor with a toner by a developing device, and recycling collected used toner to the developing device. The recycling includes driving a powder conveying pump to convey the collected used toner to the developing device when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, and determining a predetermined coefficient according to toner density of a developer of the image forming apparatus and correcting each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
According to still another preferred embodiment of the present invention, an electrophotographic image forming method includes developing a latent image formed on a photoconductor with a toner by a developing device, and recycling collected used toner to the developing device. The recycling includes driving a powder conveying pump to convey the collected used toner to the developing device when an integrated value of predetermined numerical values, each based on a number of picture elements of an image to be formed, is equal to or greater than a constant value, adding a predetermined constant value to the integrated value when driving of the photoconductor is detected, and determining a predetermined coefficient according to toner density of a developer of the image forming apparatus and for correcting each of the predetermined numerical values by multiplying the each of the predetermined numerical values by the coefficient.
In the above-described image forming methods, in the determining step the coefficient may be determined according to a difference between the toner density of the developer and a target value for the toner density. Further, in the driving step the powder conveying pump may be stopped to be driven a predetermined time after having been started to be driven.